JP2000290902A - Railroad sleepers made of foamed polymer products - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a plastic sleeper which does not require costly fiber reinforcement, does not rot, and has excellent durability. SOLUTION: A polyisocyanate having an isocyanate-terminated prepolymer as a main component obtained by reacting polyoxypropylene diol with diphenylmethane diisocyanate, and a polyol having a hydroxyl value of 300 to 500 and having a polyfunctional polyol having 4 or more functional groups as a main component. Wherein the blowing agent is one or more selected from water, hydrocarbons and halogenated hydrocarbons.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic sleeper.

[0002]

2. Description of the Related Art A railroad sleeper serves to support rails, transmit wheel pressure to a roadbed over a wide area, and maintain a constant rail gauge. Conventionally, hardwood squares such as chestnuts and hinoki have been used as sleepers.

Further, concrete sleepers have been used because of the difficulty in obtaining wood and the short life. However, those made of concrete, the strength is excellent in durability, because the elastic in comparison with the wood is very small, inevitably elastic rubber sheet or the like is required to compensate for this. Furthermore, the workability is poor because the weight is larger than wooden.

[0004] For this reason, plastic sleepers containing foamed polyurethane as a main component have recently been manufactured.

[0005]

However, this sleeper made of foamed polyurethane is only made of urethane foam.
It is difficult to obtain the required strength, and reinforcement is made with long fiber glass fibers or the like.

[0006] Although fiber reinforcement increases the strength as described above, the cost is significantly increased and the cost is considerably higher than wooden or concrete sleepers. Further, in order to prevent an increase in the cost of fiber reinforcement, it is conceivable to additionally laminate layers having different properties.

[0007]

Means for Solving the Problems In view of the above-mentioned situation, the present inventor has completed an inexpensive plastic sleeper which does not require fiber reinforcement as a result of intensive studies. Polymerization product of a polyisocyanate having an isocyanate-terminated prepolymer as a main component obtained by reacting polyoxypropylene diol and diphenylmethane diisocyanate with a polyol having a hydroxyl value of 300 to 500 and having a polyfunctional polyol having 4 or more functional groups as a main component. Wherein the blowing agent is one or more selected from water, hydrocarbons and halogenated hydrocarbons.

The first feature of the present invention resides in that a prepolymer is used. That is, since polyurethane is produced by polymerization of isocyanate and polyhydric alcohol, it is usually polymerization of monomers. What is new is that this is not a isocyanate monomer but a prepolymer. That is, the properties required for the sleepers have become closer to those of the conventional wooden materials due to such a device.

The prepolymer used in the present invention is obtained by reacting polyoxypropylene diol with diphenylmethane diisocyanate (MDI). The polyoxypropylene diol preferably has a number average molecular weight of 400 to 2,000. When it is less than 400, the compression modulus is too large, and when it is more than 2,000, the bending strength decreases. Also,
The NCO content of this prepolymer is preferably between 5 and 35%.
This is the degree of flexibility and bending strength that best fits the sleepers. This is due to the structure of the polymer by polymerization.

As the isocyanate component which undergoes a urethane reaction, only the above-mentioned prepolymer may be used, or another isocyanate component having good compatibility with this prepolymer may be mixed. An example is crude MDI. This M
DI has an NCO value of about 2 to 3. The mixing ratio is preferably equal to or less than that of the prepolymer. As described above, when a low molecular isocyanate is mixed as the isocyanate component, the bending strength becomes larger,
In addition, the bending strain was smaller.

The polyol to be reacted with the above prepolymer is mainly composed of a polyether polyol having a hydroxyl value of 300 to 500 and having four or more functional groups. Further, similarly to the above isocyanate component, another component may be mixed.
As the polyol to be mixed, a diol having a molecular weight of 150 or less is preferable. When a low molecular diol is mixed, the bending strength is further improved. This also requires compatibility between the polyols as described above.

The reason for using such a polyol having four or more functional groups is that, in the case of a commonly used trifunctional or lower functional group (such as a glycerin type), the bending strain of the polymer is large (too soft). Plug) has low pull-out strength. For this reason, there was a problem in the function of fixing the rail as a sleeper.

As for the degree of foaming, the density of the foam is 0.1%.
Adjust so as to be ⁵ to 1.0 g / cm ³ .

Further, in order to lower the compression modulus, a soft phase which is a polymer gel may be dispersed in the foam. This is incompatible with the above-mentioned polyol component and has a number average molecular weight of 1,000 to 10,000 and a hydroxyl value of 10 to 20.
About 0 polyol is dispersed in the polyol,
It can be manufactured by polymerization. This means that there is a chemical bond between the foam and the soft phase, so that the overall mechanical strength is not impaired and the flexibility is further improved.

The sleeper of the present invention can be used alone like a wooden sleeper, but may be laminated with an elastic material such as a vibration-proof rubber to further improve vibration absorption and the like.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail based on embodiments of the present invention. First, physical properties required for a sleeper will be described. 1) Flexural strength (kg / cm ² ): This is the difficulty of breaking the sleepers and the resistance to bending force. That is, it is bending strength. Of course, the larger the better. Measurement method: Measured according to JIS K7221. 2) Compression modulus (kg / cm ² ): This indicates hardness, and the softer and better the sleeper, the better. Measurement method: Measured according to JIS K7220. 3) Proportional compression limit (kg / cm ² ): This is the force up to the limit at which elasticity is lost. Measurement method: Measured according to JIS K7220. 4) Density (g / cm ³ ): about 0.5 to 1.0 is preferable. Measurement method: Measured according to JIS Z8807. 5) Pull-out strength (ton): This is the force when pulling out the anchor nut to fix it to the embedded anchor nut with bolts. Of course, the larger the better. Measurement method: Measured according to JIS E1118 and JIS E1201.

The sleepers of the example of the present invention and the comparative example were prepared, and the above physical properties were compared. Example 1 Isocyanate component: a reaction product of polyoxypropylene glycol having a number average molecular weight of 1,000 and diphenylmethane diisocyanate, and having an NCO component content of 17.5.
% Stuff. Polyol component: a polyether polyol having four or more functional groups and having a hydroxyl value of about 400. Blowing agent: water

Example 2 Isocyanate Component 1: A reaction product of polyoxypropylene glycol having a number average molecular weight of 1,000 and diphenylmethane diisocyanate, and having an NCO component content of 17.
5% thing. Isocyanate component 2: Crude diphenylmethane diisocyanate having an NCO content of 31%. Polyol component: a polyether polyol having four or more functional groups and having a hydroxyl value of about 400. Blowing agent: water

Comparative Example Isocyanate component: crude MDI (diphenylmethane diisocyanate) polyol component: tetrafunctional polyether polyol Blowing agent: water

These were polymerized and their physical properties were measured.
Table 1 shows the results. The table also shows those made of wood and concrete.

[Table 1]

In this table, specimens were prepared so as to have the same bending strength except for those made of wood and concrete, and compared.
Examples 1 and 2 both have very small compression elastic moduli,
It can be seen that it is softer and has better cushioning properties than ordinary urethane. It goes without saying that concrete is bad and wood is excellent. However, it can also be seen that the invention is closer to wooden than to concrete. Further, other physical properties are almost excellent, and it can be seen that the sleeper is superior to ordinary urethane. Since the specific gravity is less than or equal to that of wooden sleepers, and the proportional compression limit is larger than that of wooden sleepers, the residual strain due to the weight of railway vehicles is smaller than that of wooden sleepers. Also, since there is no need to perform fiber reinforcement, the cost can be considerably lower than that of a plastic sleeper that requires fiber reinforcement.

The most important physical property, pull-out strength, also has a large difference (close to concrete), but this is not only a numerical difference but in Examples 1 and 2, the anchor nut was just pulled out. However, in the comparative example, when the anchor nut was pulled out, the main body cracked from that portion and was broken. Therefore, in the example, the detached portion is cut into a cylindrical shape, and can be repaired by filling with an adhesive or a filler and filling the anchor nut, whereas in the comparative example, the repair is almost completed because the main body is broken. Impossible. This difference is very large and will be critical at track repair sites.

[0023]

According to the sleeper of the present invention, there are the following significant advantages. 1) Because it is made of plastic, there is no rot like wood. 2) Strength is close to concrete sleepers. 3) The residual strain due to the compressive load of railway vehicles is smaller than that of wooden sleepers. 4) Compared to other plastics, it does not require fiber reinforcement, so it is more economical.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akihiro Taka 1-13-28 Minamikaneda, Suita-shi, Osaka Toyo Polymer Co., Ltd. (72) Inventor Akira Murakami 1-13-28 Minamikaneda, Suita-shi, Osaka Inside Toyo Polymer Co., Ltd.

Claims (5)

[Claims] 1. A polyisocyanate having an isocyanate-terminated prepolymer obtained by reacting polyoxypropylene diol and diphenylmethane diisocyanate as a main component, and a polyol having a hydroxyl value of 300 to 500 and having a polyfunctional polyol having 4 or more functional groups as a main component. Wherein the foaming agent is one or more selected from water, hydrocarbons and halogenated hydrocarbons, the railroad sleeper made of a foamed polymerization product. 2. The polyisocyanate is obtained by adding crude MDI to the prepolymer.
A railroad sleeper made of the foamed polymerization product of the above. 3. The railroad sleeper made of a foamed polymerization product according to claim 2, wherein the polyol further comprises a diol having a molecular weight of 150 or less. 4. The prepolymer comprises 5 to 3 NCO components.
The railroad sleeper made of a foamed polymerization product according to claim 2, which is 5%. 5. The railroad sleeper made of a foamed polymerization product according to claim 1, wherein the flexible phase as a polymer gel is present in a dispersed state in the foamed body.